Three rare etiologies of urinary retention in pediatrics: A case series and review of the literature

Key Clinical Message Etiology of urinary retention in pediatric age differs significantly from adults and the elderly. Therefore, a comprehensive diagnosis is crucial before specific treatment. Every effort must be made to minimize invasive procedures as far as possible in children.


| INTRODUCTION
][4] Generally, UR can be divided into acute and chronic forms.In contrast to chronic UR, which mostly presents painlessly, AUR is often a painful condition. 5Although there are several classification systems, pediatric UR is often classified according to the underlying etiology.Mechanical, inflammatory, infectious, neurologic and behavioral etiologies have been reported in the literature. 3revious studies have suggested mechanical etiologies as one of the most prevalent causes of pediatric AUR. 2,3n this study, we presented three uncommon and complex mechanical types of AUR in children.These included a bladder diverticulum, a Müllerian duct cyst (MDC), and a ureteral stump syndrome.We then reviewed the literature, described existing treatment modalities and delineated our management strategy.This manuscript was prepared following the CARE guidelines (https:// www.cares tatem ent.org).

| Bladder diverticulum
The patient was a 14-month-old male infant with AUR.Upon further workup, we found that the boy had been experiencing voiding difficulties since birth.Abdominopelvic ultrasonography (US), voiding cystourethrography (VCUG), and urodynamic studies (UDSs) were performed for the patient.Abdominopelvic US and VCUG studies revealed remarkable compression caused by a bladder diverticulum at the level of the bladder neck and posterior urethra, hampering successful voiding despite bladder fullness and the patient straining to void.Additionally, an ipsilateral vesicoureteral reflux (VUR) was observed (Figure 1).
Open surgical resection, utilizing intra-and extravesical approaches, was performed for him (Figure 2).The ureter was then reimplanted.The operation was uneventful, and the patient voided freely after postsurgical foley catheter removal.We followed the patient with a UDS 6 months after surgery.The UDS was mostly normal (i.e., normal bladder compliance, no sign of bladder over activity, PdetQmax = 64 cmH 2 O, Qmax = 21 mL/s) except for some degree of dysfunctional voiding.Follow-up abdominopelvic USs were also performed every 6 months, and he had four normal abdominopelvic USs after the operation.Findings from the last abdominopelvic US were as follows: no sign of hydroureteronephrosis, bladder wall thickness = 4.5 mm, post-void residue (PVR) = 10 mL.A uroflowmetry was also performed on the latest follow-up which was satisfactory (i.e., Qmax = 23 mL/s).

| Müllerian duct cyst
The patient was a 3-day-old boy with AUR who was unable to void and had dribbling since birth.When the urethral catheter insertion failed, a cystostomy tube was inserted for him.The patient then underwent an investigational cystoscopy, where a large obstructing mass in the posterior urethra and bladder neck with severe bladder trabeculation was observed.An internal foley catheter was inserted during cystoscopy, and the patient underwent further workup (Table 1).Findings of our initial VCUG (Figure 3A,B) and initial magnetic resonance urography (Figure 3C) confirmed the presence of a large obstructing cystic lesion without any solid components at the level of the bladder neck.
Based on the patient's age and acute symptoms, we performed transurethral cyst aspiration after completing his workup in the second week of life.The neonate could void after the first procedure but in an interrupted pattern.Therefore, we started clean intermittent catheterization (CIC) and reevaluated the patient at the age of 3 months.The baby had no episodes of urinary tract infection (UTI) 3 months after the initial transurethral cyst puncture.Abdominopelvic US also showed remarkable improvement in hydronephrosis on both sides.We performed a second-look cystoscopy at the age of 11 months.The cyst remnant was visible at the prostatic urethra, but its volume decreased remarkably.We performed aspiration and multiple punctures at the dependent part of the cyst in the prostatic urethra.The aspirated fluid was light yellow, F I G U R E 1 A large bladder diverticulum with ipsilateral vesicoureteral reflux (Grade 3) which compressed the bladder neck and posterior urethra during voiding.A narrow urethral course due to weak and poor contrast flow is notable; red star: urinary bladder, yellow star: bladder diverticulum, green arrow: urethra.and cytological evaluation revealed no malignant cells or any types of germ cells.The baby was CIC-free after the second procedure.
One year after the second aspiration procedure, the first follow-up VCUG was obtained which showed a notable improvement in VUR grade on both sides.Initially, the VUR grade was 5 on both sides before the initial cyst puncture and aspiration (Figure 3A,B) but improved to Grade 3 on the right side and Grade 2 on the left side after the two consecutive procedures (Figure 3D).A dimercaptosuccinic acid (DMSA) renal scan was also obtained which did not demonstrate any new renal scar.The patient's VUR completely resolved by age 3 as evaluated by a second follow-up VCUG (Figure 3E).In the last follow-up visit, the child had an acceptable urine stream and a PVR of less than 5 mL was reported in the abdominal US.The patient has not had any urinary retention episodes and has been UTI-free after the second aspiration procedure.

| Ureteral stump syndrome
A 3-year-old boy with a right-sided single functional kidney and hydronephrotic kidney with an obstructingrefluxing megaureter on the left side has been under routine follow-up due to antenatal hydronephrosis and voiding dysfunction.The patient received prophylactic antibiotic therapy due to Grade 5 VUR on the left side and poor functioning hydronephrotic kidney (less than 10%) until the age of 2. The boy suffered repetitive episodes of UTI when he started toilet training at age 3. His UTIs could not be controlled with prophylactic antibiotics, changing his voiding behaviors, or even by performing a complete course of biofeedback therapy.The patient also had high PVR due to high-grade VUR.At this stage, a cystourethroscopy was planned to better evaluate the abnormally high PVR and assess for possible urethral pathology.The left ectopic ureter was located at the posterior urethra just below the bladder neck with a relatively normal-appearing opening.A new DMSA renal scan revealed a hydronephrotic left kidney with less than 5% activity.Therefore, we planned a nephrectomy with a partial ureterectomy. 6,7e did not perform an extensive dissection beneath the bladder neck, trigone, and posterior urethra to remove the ureter completely; as an extensive dissection of these areas could predispose the patient to further voiding dysfunction.After the surgery, the patient experienced a decrease in his urine stream compared to his preoperative condition and developed repeated episodes of UR.Consequently, our patient was started on CIC therapy.Abdominopelvic US and VCUG were performed.VCUG revealed a refluxing dilated ureteral stump, with a ureteral orifice located in the posterior urethra, which caused narrowing of the posterior urethra and compressed the bladder neck during micturition (Figure 4).
Surgical removal of the ureteral stump was planned.The distal part of the stump was dissected from the surrounding tissues.The ureteral stump was then opened; utilizing a longitudinal incision on its ventral aspect down to the bladder neck level.Thus, we accessed the ureteral orifice using an intraluminal approach.Lastly, at the level of ureteral insertion into the posterior urethra, we oversewn the orifice with an absorbable suture and excised only the mucosal layer of the distal part of the ureteral stump.This method avoids extra dissection of the area beneath the trigone, the bladder neck, and the posterior urethra.The patient was symptom-free and had no other UR incidences during the 5-year follow-up.Table 1 provides a succinct timeline of the patients' evaluation, therapeutic management, and postoperative follow-up.

| DISCUSSION
UR is relatively rare in pediatric age.A wide variety of etiologies have been attributed to causing AUR in children.For instance, in a study by Nevo et al. 3 on 56 children with UR, the authors reported that mechanical obstruction (25%) was the most common cause of UR, followed by infectious/ inflammatory causes (18%), fecal impaction (13%), neurologic diseases (11%), gynecologic pathologies (7%), and behavioral etiologies (5%).In a more recent and larger study by Schmidt et al. 2  as the causes of AUR.This wide variety of etiologies and their complex nature, usually calls for a comprehensive diagnostic approach including VCUG, Abdominopelvic US, computed tomography (CT), magnetic resonance imaging (MRI), and occasionally, endoscopic investigation, to identify the underlying pathology.
In the present study, we presented three rare cases of mechanical UR in children.We discussed their etiologies with the subsequent managements and reviewed the previous evidence in each case.In order to conduct a thorough literature review, the previous studies on UR caused by bladder diverticulum, MDC, and ureteral stump syndrome in children were found by searching the following keywords in PubMed (March 2023): ("Urinary Retention"[MeSH Terms] OR "retention*"[Title/ Abstract]) AND ("diverticul*"[Title/Abstract] OR "mullerian*"[Title/Abstract] OR "stump*"[Title/Abstract]). Additional articles were added from the bibliography of the retrieved manuscripts.Only English articles were included.Studies which included patients above 18 years of age, reported UR due to other etiologies, or their full text was not accessible, were excluded.With regards to bladder diverticula causing UR, 20 articles, including 49 cases, were found, while only four articles, including five cases, were found for MDC.  Beses, no report for UR due to ureteral stump syndrome was found with the mentioned keywords.

| Bladder diverticulum
According to the literature, at least four different types of bladder diverticula (i.e., congenital, acquired, iatrogenic, and syndromic) can be identified in pediatric

F I G U R E 4
Large refluxing-obstructing ureteral stump compressed bladder neck and posterior urethra.After catheter removal, the patient could not accomplish a voiding cliché.Therefore, urethral visualization/evaluation was performed using a retrograde approach.Red star: urinary bladder, yellow star: ureteral stump, green arrow: urethra.age group.Congenital bladder diverticula are mucosal protrusions through the weak points of detrusor muscle.They are relatively rare in children (0.7%-1.7%) and usually occur in men. 16,323][34][35][36] A low-lying congenital bladder diverticulum may cause bladder outlet obstruction; by impinging on the bladder neck and urethra after being filled with urine. 37Acquired bladder diverticula occur due to an aberrant increase in intravesical pressure.Anatomical or functional obstruction is the primary cause of this type of obstruction.These patients usually have simultaneous voiding symptoms, such as urgency, frequency, hesitancy, and abdominal voiding.Iatrogenic diverticula are rare and usually occur following ureteral reimplantation, cystostomy tube insertion, rectovesical fistula repair, and other surgical interventions on the urinary bladder. 38The last type of bladder diverticula exist in syndromic conditions, such as prune belly syndrome, Williams syndrome, and Ehlers-Danlos syndrome. 13ost studies concur on the efficacy of VCUG as a suitable diagnostic method in these patients.Voiding plains must be obtained, as in some cases, the bladder diverticulum can only be detected on voiding images.Oblique images are also advised for better anatomical demonstrations. 28Additionally, Garat et al. 34 suggested that pre-and postoperative UDSs can be obtained in primary (nonobstructive) congenital bladder diverticula to better evaluate the associated functional or anatomical abnormalities.
Congenital bladder diverticulum treatment must be individualized.Asymptomatic children, especially those without ipsilateral VUR, can be kept under observance.Intervention should be reserved for children who exhibit symptoms related to the bladder diverticulum.Expectant management is also preferable in patients with congenital connective tissue abnormalities, such as Menkes' or Ehlers-Danlos syndromes.][41] Surgical intervention should be considered in symptomatic bladder diverticula patients.Although transurethral procedures are not commonly employed, 37 some studies have reported notable outcomes following endoscopic fulguration of bladder diverticula in adult patients. 42,43Surgical excision of the bladder diverticulum by open or laparoscopic/robotic approaches is the recommended treatment for symptomatic patients.The transvesical approach allows complete resection of the bladder diverticulum and possible ureteral reimplantation.In huge bladder diverticula, a combination of extra-and intravesical approaches may also be used. 12,33,34aparoscopic surgery, 44,45 pneumovesicoscopic surgery, 46 and robotic-assisted diverticulectomy 47 are all acceptable modalities for bladder diverticulum excision.Ureteral reimplantation has not been advised for all patients except those with ipsilateral VUR.Cutaneous vesicostomy is the primary treatment for symptomatic neonates or very young children, and diverticulectomy is postponed until the first year of life. 12In these patients, the physician should carefully observe the postoperative intravesical pressure because removal of the diverticulum and the subsequent reduction in the overall bladder capacity can significantly increase it.

| Müllerian duct cyst
Müllerian duct anomalies result from abnormal development and fusion of the Müllerian ducts in females and failure of complete regression in males.Sertoli cells excrete the Müllerian inhibiting substance (MIS), which causes Müllerian duct regression in the male fetus.Abnormalities in MIS production, timing of its production, and/or its receptors may lead to Müllerian duct abnormalities and cystic malformations in the male fetus.When referring to these midline cystic malformations of the prostate, previous studies have mostly used the terms MDC and prostatic utricular cysts (PUC) interchangeably.Nevertheless, histologic evaluations of these lesions have suggested that MDCs and PUCs may be distinct pathologic entities. 9,48These controversial views reached a peak when Kato et al. 49 examined five adult cases with midline prostatic cystic lesions immunohistochemically and suggested that there is no evidence to assure that MDCs are actually remnants of the Müllerian ducts and even demonstrated that these cystic lesions probably originate from the prostatic utricle itself.However, pathologic evaluations of excised midline cysts have been inconsistent with some demonstrating a cubo-columnar epithelial lining comparable to that of the Müllerian ducts, 9,48 while others reporting a low cuboid to stratified epithelium identical to that of the prostatic utricle. 49It is noteworthy that most studies concur on the triple embryologic origin (i.e., urogenital sinus, Wolffian duct, and Müllerian duct) of the prostatic utricle. 50,51These multiple embryologic origins can justify the variation in histopathologic findings of cystic lesions in different studies.
MDC is a relatively rare congenital anomaly with a reported 1%-5% prevalence in male autopsies. 52,53It usually has no open communication with the posterior urethra and is only attached to the prostatic utricle through a fibrous cord-like structure. 49,52The anatomy of the verumontanum is normal in this condition. 49The clinical presentation is varied, including obstructive and irritative lower urinary tract symptoms, UTI, constipation, abdominal pain, hematuria, and ejaculatory problems. 54,55Although patients with MDC usually become symptomatic in the third or fourth decades of life, pediatric patients may also present with a wide variety of MDC-related symptoms (e.g., urinary retention, epididymitis) and even suffer from malignant transformation of these cysts. 9,31,53,56iagnosis of MDC can be challenging in infants.Many differential diagnoses must be considered and ruled out in a boy with a midline cystic lesion, including bladder diverticulum, ureterocele, seminal vesicle or ejaculatory duct cyst, prostatic cyst or abscess, rectal duplication cyst, retroperitoneal tumor, and hydatid cyst. 54Abdominopelvic US is usually the initial step of diagnostic evaluation.VCUG and retrograde urethrography are other valuable diagnostic modalities.However, transrectal US and pelvic MRI with an endorectal coil are the best imaging modalities for periprostatic and midline pelvic cysts. 57hile small asymptomatic cysts are mostly managed conservatively, surgical intervention is warranted in symptomatic patients.Several management strategies have been described in the literature.Open surgery using different approaches (i.e., extravesical or intravesical, transperitoneal, perineal, transrectal, and pararectal) has been performed by several surgeons.Laparoscopic or robotic excision of MDC has also been utilized. 9,58Moreover, endoscopic approaches have been utilized in the forms of transurethral aspiration, cold knife incision, fulguration, and dilatation of the utricle. 55,59,60There is also a report of trans-perineal aspiration and sclerotherapy under the guidance of US with successful results. 61

| Ureteral stump syndrome
Ureteral stump syndrome is considered to be a rare pathology with an incidence of only 0.8%-1%.Of these, 1.1%-10% ultimately need intervention. 62While some urologists favor complete removal of the refluxing/obstructing ureters, 63 others argue that partial ureterectomy may be a more suitable choice owing to less complicated surgical method and comparable complications rate. 7evertheless, the remaining ureteral stump in partial ureterectomy can cause complications.[65][66][67][68] Different approaches for the management of symptomatic ureteral stumps have been introduced.While open and laparoscopic surgeries for stump removal are widely practiced, 6,64,65,69 some authors have also reported less invasive approaches.[72]

| CONCLUSION
The prevalent causes of pediatric urinary retention differ from those of the adults.A wide variety of etiologies, ranging from benign behavioral and simple congenital causes to utterly complex anatomical abnormalities or even malignant transformations, can lead to pediatric urinary retention.Considering the complexity of many of these etiologies, their management should be individualized.

F I G U R E 2
Intraoperative images of bladder diverticulum resection; red star: urinary bladder, yellow star: bladder diverticulum, blue arrow: ureter.

F
I G U R E 3 (A, B) Huge obstructing cystic lesion at the level of the bladder neck with bilateral high-grade vesicoureteral reflux (VUR).(C) Magnetic resonance (MR) urography showing cystic lesion arising from the posterior urethra, compressing the posterior urethra and bladder neck.The lesion did not contain any solid components.(D) First follow-up voiding cystourethrography (VCUG) showed that the grade of VUR on both sides decreased remarkably, with acceptable contrast flow in the urethra and outpouching of the nonobstructive/ empty Müllerian duct cyst (MDC) remnant at the level of the bladder neck and posterior urethra.(E) Second follow-up VCUG performed 3 years postoperatively.Red star: urinary bladder, yellow arrow: MDC, green arrow: urethra.